import java.util.Arrays;

// 大根堆
public class PriorityQueue {
    public int[] elem;
    public int usedSize;

    public PriorityQueue() {
        this.elem = new int[10];
    }
    public void initElem(int[] array){
        for (int i = 0; i < array.length; i++) {
            elem[i] = array[i];
            usedSize++;
        }
    }
    /**
     * 建堆的时间复杂度：
     *
     * @param 
     */
    public void createHeap() {
        for (int parent = (usedSize - 1 - 1) / 2; parent >= 0; parent--) {
            shiftDown(parent,usedSize);
        }
    }
    private void swap(int chlid,int parent){
        int tmp = elem[chlid];
        elem[chlid] = elem[parent];
        elem[parent] = tmp;
    }
    /**
     *
     * @param parent 是每棵子树的根节点的下标
     * @param len  是每棵子树调整结束的结束条件
     * 向下调整的时间复杂度：O(logn)
     */
    private void shiftDown(int parent,int len) {
        int child = 2*parent + 1;
        while(child < len){
            if(child + 1 < len && elem[child] < elem[child + 1]){
                child += 1;
            }
            if(elem[child] > elem[parent]){
                swap(child,parent);
                parent = child;
                child = 2*parent + 1;
            } else {
                break;
            }
        }
    }


    /**
     * 入队：仍然要保持是大根堆
     * @param val
     */
    public void push(int val) {
        if(isFull()){
            elem = Arrays.copyOf(elem,elem.length*2);
        }
        this.elem[usedSize] = val;
        shiftUp(usedSize);
        usedSize++;

    }

    private void shiftUp(int child) {
        int parent = (child - 1) / 2;
        while(child > 0){
            if(elem[child] > elem[parent]){
                swap(child,parent);
                child = parent;
                parent = (child - 1) / 2;
            } else {
                break;
            }
        }
    }

    public boolean isFull() {
        return usedSize == elem.length;
    }

    /**
     * 出队【删除】：每次删除的都是优先级高的元素
     * 仍然要保持是大根堆
     */
    public void pollHeap() {
        if(isEmpty()){
            return;
        }
        swap(0,usedSize -1);
        usedSize--;
        shiftDown(0,usedSize);

    }

    public boolean isEmpty() {
        return usedSize == 0;
    }

    /**
     * 获取堆顶元素
     * @return
     */
    public int peekHeap() {
        if(isEmpty()) {
            return -1;
        }
        return elem[0];
    }
}